#include<bits/stdc++.h>

using namespace std;

ifstream in("biconex.in");
ofstream out("biconex.out");

const int NMAX = 100000;

vector<pair<int,int>> G[NMAX+2], GP[NMAX+2], init[NMAX+2];
bool viz[NMAX+2];
int ctc[NMAX+2], ind_ctc = 0, special_comp[NMAX+2];
vector<int> order, my_comp;
vector<pair<int,int>> adia[NMAX+2];
int artifact[NMAX+2];
int N, M;
vector<vector<int>> sol;

void dfs_plus(int nod)
{
    viz[nod] = 1;
    for( auto pp : G[nod] ) {
        int x = pp.first;
        if( viz[x] ) continue;
        dfs_plus(x);
    }
    order.push_back(nod);
}

void dfs_minus(int nod)
{
    viz[nod] = 1;
    ctc[nod] = ind_ctc;
    my_comp.push_back(nod);
    for( auto pp : GP[nod] ) {
        int x = pp.first;
        if( viz[x] ) continue;
        dfs_minus(x);
    }
}

void DFS(int nod, int gasit = 0, int tata = -1)
{
    gasit |= special_comp[nod];
    artifact[nod] = gasit;
    for( auto pp : adia[nod] ) {
        int x = pp.first;
        int z = pp.second;
        if( x == tata ) continue;
        DFS( x, gasit | z, nod );
    }
}

int main()
{

    in >> N >> M;
    for( int i = 1;  i <= M;  ++i ) {
        int x,y,z = 0;
        in >> x >> y;
        init[x].push_back({y,z});
        init[y].push_back({x,z});
    }
    memset(viz, 0, sizeof(viz));
    for( int i = 1;  i <= N;  ++i ) {
        if( !viz[i] )
            dfs_plus(i);
    }
    memset(viz, 0, sizeof(viz));
    reverse(order.begin(), order.end());
    for( auto x : order ) {

        if( !viz[x] ) {
            ++ind_ctc;
            my_comp.clear();
            dfs_minus(x);
            if( my_comp.size() > 1 )
                sol.push_back(my_comp);
        }

    }
    for( int i = 1;  i <= N;  ++i ) {
        for( auto edg : G[i] ) {
            int x = edg.first;
            int z = edg.second;
            if( ctc[x] == ctc[i] ) {
                if( z ) special_comp[ ctc[x] ] = 1;
            }
            else {
                adia[ ctc[i] ].push_back({ ctc[x] ,z});
                adia[ ctc[x] ].push_back({ ctc[i] ,z});
                sol.push_back({i, x});
            }
        }
    }
    out << sol.size() << '\n';
    for( auto& ln : sol ) {
        for( auto& x : ln ) out << x << ' ';
        out << '\n';
    }
    return 0;
}